This study is part of a 15-year project to develop less invasive methods to diagnose pneumocystis pneumonia and to predict responses to therapy. Oral washes, induced sputum, and bronchalveolar lavage are being collected from patients with immunosuppressive diseases and respiratory syndromes. During this trial resulting studies have moved the field from a focus on tissue to a focus on respiratory secretions, especially secretions that can be obtained non-invasively. Samples for control patients are being collected as well. First, a polymerase chain reaction (PCR) technique using a unique major surface glycoprotein primer was assessed in conjunction with a published primer to develop a method adaptable to clinical laboratories that is highly specific and sensitive. It is hoped that oral wash can replace sputum as the sample of choice. Second, mutations associated with drug resistance are being assessed in all organisms identified to determine the epidemiology and clinical importance of such mutations. Third, markers of strain variation are being assessed to elucidate pathogen epidemiology. A prospective trial evaluating the utility of quantitative PCR is almost completed in conjuction with the University of California-San Francisco.